The present invention relates specifically to acoustic buoys used for the detection of submarines and is more specifically aimed at improvements made to energy generators initiated by sea water, powering these buoys with electricity.
Sonobuoys, of the character known in the prior art, are generally dropped from an aircraft and include, in their utilization position, a floatation member, filled during the aerial drop of the Sonobuoy, or on impact on the water.
This flotation member supports a sealed compartment containing the electronics for buoy-aircraft linkage, from which an electro-carrier cable leads out, supporting a load immersed to a depth selected before the drop (50 or 150 m for instance).
The load consists of a sonar comprising an electro-acoustic transducer and the associated electronics (transmitter and receiver for active sonar).
The sonar is supplied with electric power by a generator or an ignitable battery, with sea water used as electrolyte.
For some Sonobuoys of the character known in the prior art, the generator is arranged on the flotation member, and the electric energy is transmitted to the sonar via the electro-carrier cable.
To facilitate assembly, maintenance and wiring of the buoy, it is proposed to house the ignitable generator near the sonar at the cable end and, more specifically, to attach said generator directly to the electro-acoustic transducer.
However, although this solution offers the desired simplification advantages, it is evident that it does lead to unexpected drawbacks in some operating conditions. Indeed, during the operation of a Sonobuoy arranged according to said solution, the presence of interference noise has been noted, disturbing operation of the Sonobuoy and preventing satisfactory processing in the aircraft of the sonar signals transmitted by the buoy. The origin of this interference noise was difficult to discover but finally, it was recognized that the interference noise was generated when the electro-acoustic transducer of the buoy came into contact with bubbles emitted by the energy generator.
Indeed, the type of ignitable battery used in this application is a high power generator in terms of mass and volume (for instance 700 W per liter), in which chemical reaction leads to the giving off of substantial amounts of gases which escape from the battery into the sea water in the form of a multitude of bubbles.
In rough seas, the transducer and battery ascend and descend (heaving motion), so that the ascentional speed of the transducer in some cases exceeds the ascential speed of the bubbles. This means that the transducer catches up with the bubbles, so that, when they come into contact with it, intereference signals are generated.